Humbrol used to do an 'Authentic Colour' in RLM02, and I've still got a usable tin! BUT, I've seen varying shades of the actual colour. One, like the Humbrol mentioned, is more of a green/grey, not unlike the shade used as 'Field Grey' on Wehrmacht uniforms, as used on upper surface camouflage schemes, such as the BoB Bf109's, whilst another is a much lighter shade of grey-green.
Until I realised I still had some 02, I'd mixed my own, using Humbrol Matt Dark green 30, Matt Dark Grey 27, and white. The ratios were roughly:- Green and Grey 50/50, add white at about 25% to the above mix.